Maximal Exercise Test - The subject pedals on a stationary bicycle for about 10 minutes. After a 3-minute warm-up, the workload is increased continuously until either the subject can no longer continue or the physician stops the test for medical reasons. During the exercise, heart rate and heart activity are monitored with an EKG, and the subject wears a nose clip and mouthpiece connected to a breathing tube to measure oxygen use. Blood is drawn before and during the test, totaling no more than 2 tablespoons.